Dwell-cam



2 Shets-Shee t 1. J. THOMSON. DWELL 0AM.

(No Model.)

No. 378,343. Patented Feb. 21. 1888.

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(No Model.) 2 Shess-Sheet 2.

J. THOMSON.

DWELL 0AM.

No. 378,343. Patented Feb. 21, 1888.

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Uwrrnn STATEs PATENT JOHN THOMSON, OF BROOKLYN, NEW YORK, ASSIGNOR TO THE OOLTS PATENT FIRE ARMS MANUFACTURING COMPANY, OF HARTFORD,

CONNEOTICUT.

DWELL-CAM.

SPECIFICATION forming part of Letters Patent N0. 378,343, dated February 21, 1888.

Application filed October 12, 1887. Serial No. 252,174. (No model.)

To aZZ 2071 0117, it may concern:

Be it known that 1, JOHN THOMSON, a citizen of the United States, and a resident of Brooklyn, Kings county, New York, have invented certain new and useful Improvementsin Dwell- Cams and Bearings Therefor, of which the fol' lowing is a specification.

This invention relates to cams of that class generally known to the trade as dwell-cams when applied to presses and similar machines in which the motion of one portion of the press or other machine is produced by direct-acting cranks, the main connecting-rods being slotted at the crank-pin eyes,so as to permit the crankpins to traverse the slots, during which time the cams act to control the action of the press.

The object of the present invention is to improve the operation and increase the durability of actions of this class.

In the drawings, Figure 1 is an elevation showing the application of my invention to an oscillating-platen press. Fig. 2 is a top plan view and horizontal section of the same. Fig. 3 is a detached view of the crank-pin eyes of main connecting-rods; and Fig. 4 is an illustration of the cam known in the market as The Colts Armory Style, and which repre sents the most advanced state of the art up to the time of my improvement.

Briefly described, these cams produce the following results: During, say, sixty to sixtyfive per cent. of the time of each complete in tation of the cranks the platen is swung back or forth at the full speed of the travel of the cranks and corresponds to the circular portion of the cam, Fig. 4, between the points 5 5, while during the balance of the time the platen is controlled entirely by the cam at a speed less than thatof the travel of the cranks, and is held during a short period at a state of rest or dwcll, from whence arises the trade designation of these cams. The duty required, however, is exceedingly severe, and their use heretofore has been generally unsatisfactory, in consequence of rapid wear, which develops a jerky unsteady motion in the platen. Such failure has been almost, if not entirely, due to the necessary form of the cam, which, in view of the required conditions of its operation, has

involved too quick 2. reduction or increase, as the case may be, of the speed of the platen.

In other words, too much work has been required in too short time.

Still referring to Fig. 4, it will be observed that the friction-roller 6, which is mounted 5 upon and acts with the main connecting-rod 7, is at the extremity of the rod, the crankpin standing between the roller and the platen at all times.

In my improved device I reverse the order just described and mount the friction-roller 8 upon a stud, 9, in the connecting-rod, 10, between the crank-pin 11 and the platen 12. By this simple change of position the radius of the circular or idle portion of the cam,as from 13 to 14, (which corresponds to the motion of the platen produced at the full speed of the cranks,) is relatively somewhat greater than that shown in Fig. 4. The consequence of the change of location of the roller and the increased diameter of the circular or idle portion of the cam is that the dwell-section of the can], as at 15 16, may be formed to any curve or contour which may be desired, and within the radius of the said circular p 'ortion. This, it will be observed, is directly opposite from that shown in Fig. 4, in which the dwellsection, as 17 18, must necessarily be developed outside of or beyond the circular or idle portion of the cam.

In the cam shown in the first three figures of the drawings the action is such as to permit the platen to be driven at the full speed of the cranks until the said platen will have reached an angle of forty-five degrees, (indicated by dotted line 19,) after which time the outward motion of the platen is cumulatively decreased in speed until it reaches the extreme outer angle of, say, sixty-eight degrees, as see dotted line 20. In like manner the platen is carried forward from position 20 to that of position 19, the speed being constantly increased froma point of rest until the velocity equals that of the cranks. As a matter of fact, the cams between these positions act upon the platen diiierentially with respect to the cranks. Now,by a comparatively slight change in the dwell portion of the cam, they platen might be more quickly driven to the position indicated by the line 20, and be there maintained at a stop or dwell. It will be seen that the dwell portion of the cam always has the shortest radius in my improved con struction, instead of the longest, as in the old construction,whereb y the excessive strain due to such construction is avoided; but the illustration here presented is selected to show a condition of operation which would be impossible in the style of cam shown in Fig. 4, except by bringing the converging lines l7 18 of the dwell portion of the cam to a point, which would of course be an impracticable'construction. Another advantage of this change in the position of the stud and roller is that the rod is pierced at a position less likely to weaken it under severe strain.

It has been the usual practice heretofore to simply mill out the slot 21 of the main connecting-rod, the width of the slot being equal to the diameter of the crank-pin. In rods of this style when subjected to heavy strain, in that the crank-pin is unsupported at the back, there is greater liability to wear and out both in the crank-pin and the bearing-surfaces of the end of the slot. Therefore, in consequence of this mode of construction, and, further, in that it is usually necessary to construct these rods either of wrought iron or steel, while the crank-pins are also either of wrought iron or steel, the life of these parts is comparatively limited, and once they are worn or out there is no practicable remedy but to supply new rods or new crank-pins in lieu of the old. I obviate this difficulty by fitting to the crankpin a loose bushing, 22, of bronze, composition, or hardened steel, milling out the slot in the rod to admit its increased diameter. In this wise, under heavy impressional strain, the bushing, in consequence of its greater diameter, is prevented from turning, and thereby acts as a fixed bearing for the crank-pin. There is thus no direct abrasive action between the crank-pin and the end of the slot, and in the event of wear the old bushing may be easily and cheaply replaced by a new one. In

addition, as the crank-pin travels back and forth in the slot, the bushing acts as a frictionroller, thus changing its position and presenting its entire inner surface to the strain-bearing portion of the crank-pin.

While I have described and illustrated one form of press to which my invention is especially applicable, it is evident that the principles thereof may be readily applied to other forms of presses and other machines by those skilled in the art.

hat I claim is l. The combination, with a moving portion of a press, of a crank-pin, a slotted connecting-rod between the pin and moving portion of the press, a cam mounted on. the pin, and

a friction-roll mounted on the rod and engaging the cam and arranged between the crankpin and moving portion of the press, substan tially as described.

2. The combination, with a connecting-rod mounted on a crank-pin, of a cam secured to the pin, and a friction-roll mounted on the connecting-rod between the pin and operating end of said rod, the bearing surface of the cam at the dwell portion having the shortest radius,

substantially as described.

3. The cam, in combination with the crankpin, slotted connecting-rod, and friction-roller mounted on the rod, the dwell portion of the cam, as 15 16, being of less radius than the idle portion, as 13 14, substantially as described.

4. The combination, with the cam, the crankpin, slotted connecting-rod, and friction-roller mounted on the rod, of the bushing, as 22, mounted on the crank-pinand acting within the slot of the rod, whereby the said bushing acts alternately as a fixed bearing and as a friction-roller, substantially as described.

In testimony whereof Ihave signed my name to this specification in the presence of two subscribing witnesses.

JO HN THOMSON.

Wit nesscs:

J. S. BARKER, F. L. FREEMAN. 

